CD4 cell count at initiation of ART, long-term likelihood of achieving CD4 >750 cells/mm3 and mortality risk

OBJECTIVES

We sought to evaluate associations between CD4 at ART initiation (AI), achieving CD4 >750 cells/mm(3) (CD4 >750), long-term immunological recovery and survival.

METHODS

This was a prospective observational cohort study. We analysed data from ART-naive patients seen in 1996-2012 and followed ≥3 years after AI. We used Kaplan-Meier (KM) methods and log-rank tests to compare time to achieving CD4 >750 by CD4 at AI (CD4-AI); and Cox regression models and generalized estimating equations to identify factors associated with achieving CD4 >750 and mortality risk.

RESULTS

Of 1327 patients, followed for a median of 7.9 years, >85% received ART for ≥75% of follow-up time; 64 died. KM estimates evaluating likelihood of CD4 >750 during 5 years of follow-up, stratified by CD4-AI <50, 50-199, 200-349, 350-499 and 500-750, were 20%, 25%, 56%, 80% and 87%, respectively (log-rank P < 0.001). In adjusted models, CD4-AI ≥200 (versus CD4-AI <200) was associated with achievement of CD4 >750 [adjusted HR (aHR) = 4.77]. Blacks were less likely than whites to achieve CD4 >750 (33% versus 49%, aHR = 0.77). Mortality rates decreased with increasing CD4-AI (P = 0.004 across CD4 strata for AIDS causes and P = 0.009 for non-AIDS death causes). Among decedents with CD4-AI ≥50, 56% of deaths were due to non-AIDS causes.

CONCLUSIONS

Higher CD4-AI resulted in greater long-term CD4 gains, likelihood of achieving CD4 >750, longer survival and decreased mortality regardless of cause. Over 80% of persons with CD4-AI ≥350 achieved CD4 >750 by 4 years while 75% of persons with CD4-AI <200 did not. These data confirm the hazards of delayed AI and support early AI.

Subcutaneous IGF-1 is not beneficial in 2-year ALS trial

BACKGROUND

Previous human clinical trials of insulin-like growth factor type I (IGF-1) in amyotrophic lateral sclerosis (ALS) have been inconsistent. This phase III, randomized, double-blind, placebo-controlled study was undertaken to address whether IGF-1 benefited patients with ALS.

METHODS

A total of 330 patients from 20 medical centers were randomized to receive 0.05 mg/kg body weight of human recombinant IGF-1 given subcutaneously twice daily or placebo for 2 years. The primary outcome measure was change in their manual muscle testing score. Secondary outcome measures included tracheostomy-free survival and rate of change in the revised ALS functional rating scale. Intention to treat analysis was used.

RESULTS

There was no difference between treatment groups in the primary or secondary outcome measures after the 2-year treatment period.

CONCLUSIONS

Insulin-like growth factor type I does not provide benefit for patients with amyotrophic lateral sclerosis.

Assessment: transcranial Doppler ultrasonography: report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology

OBJECTIVE

To review the use of transcranial Doppler ultrasonography (TCD) and transcranial color-coded sonography (TCCS) for diagnosis.

METHODS

The authors searched the literature for evidence of 1) if TCD provides useful information in specific clinical settings; 2) if using this information improves clinical decision making, as reflected by improved patient outcomes; and 3) if TCD is preferable to other diagnostic tests in these clinical situations.

RESULTS

TCD is of established value in the screening of children aged 2 to 16 years with sickle cell disease for stroke risk (Type A, Class I) and the detection and monitoring of angiographic vasospasm after spontaneous subarachnoid hemorrhage (Type A, Class I to II). TCD and TCCS provide important information and may have value for detection of intracranial steno-occlusive disease (Type B, Class II to III), vasomotor reactivity testing (Type B, Class II to III), detection of cerebral circulatory arrest/brain death (Type A, Class II), monitoring carotid endarterectomy (Type B, Class II to III), monitoring cerebral thrombolysis (Type B, Class II to III), and monitoring coronary artery bypass graft operations (Type B to C, Class II to III). Contrast-enhanced TCD/TCCS can also provide useful information in right-to-left cardiac/extracardiac shunts (Type A, Class II), intracranial occlusive disease (Type B, Class II to IV), and hemorrhagic cerebrovascular disease (Type B, Class II to IV), although other techniques may be preferable in these settings.

Can we eliminate placebo in ALS clinical trials?

BACKGROUND

Previous studies concluded that the decline in strength in patients with amyotrophic lateral sclerosis (ALS) is a linear function. If so, a patient's natural history might serve as the control, instead of placebo, in a clinical trial.

METHODS

A placebo-controlled ALS clinical trial included a natural history phase, followed by a 6-month treatment phase. Each patient's forced vital capacity (FVC) score and maximal voluntary isometric contraction (MVIC) raw scores were measured monthly, standardized, and averaged into megascores. For 138 patients, the arm, leg, FVC, arm+leg combination, and arm+leg+FVC combination megascore slopes during the natural history phase and during the placebo phase were compared.

RESULTS

The mean slope of megascores during the natural history phase and the mean slope during the placebo phase were not different for the arm, leg, and arm+leg megascores, but were different for the FVC and arm+leg+FVC combination megascores.

CONCLUSIONS

Natural history controls may be useful in ALS exploratory trials that use arm megascore slope as the primary outcome measure. However, there are distinct limitations to the use of natural history controls, so that Phase 3 ALS clinical trials require placebo controls.

Environmental risk factors for amyotrophic lateral sclerosis

In order to evaluate reported associations of environmental risk factors with amyotrophic lateral sclerosis (ALS), consideration is given first to robust clinical and epidemiologic observations. These are observations which have persisted in time, have been replicated consistently and likely reflect the reality of the disease. Sporadic, familial and Western Pacific ALS are considered. In contrast, other associations appear to have emerged due to chance, sometimes compounded by faulty study design, and have dissipated once greater attention was given to methodological rigor. Current data suggest that there are no robust environmental risk factors for sporadic ALS.

Alzheimer's disease underlies some cases of complex partial status epilepticus

Alzheimer's disease is a known risk factor for seizures, and age older than 60 years is a recognized risk factor for poor outcome from convulsive and nonconvulsive status epilepticus. The authors suspect that there may be a causal relationship between dementia pathology and the development and maintenance of refractory seizures. They report two selected patients with complex partial status epilepticus whose presentation and clinical course provide partial support for this hypothesis. Their methods include case reports with clinical, EEG, imaging, and pathologic correlations. The patients were 70 and 85 years of age. Both had central and peripheral brain atrophy on imaging studies (with some regions that were affected more than others), left temporal seizure foci corresponding to areas of greatest cortical atrophy, and early presentation with inhibitory epileptic symptoms (aphasia), with evolution to complex partial status epilepticus. Pathologic confirmation of Alzheimer's disease was obtained in one patient who had not been diagnosed previously. It involved maximally the cortex underlying the seizure focus. A diagnosis of probable Alzheimer's disease was established in the other patient. Alzheimer's disease may be causal in some cases of complex partial status epilepticus. Additional observations in support of this hypothesis are needed.

Inhibitory simple partial (non-convulsive) status epilepticus after intracranial surgery

OBJECTIVES

To report on five patients who developed, 2 to 4 days after an intracranial neurosurgical procedure, new, persistent, focal neurological deficits which were due to inhibitory simple partial (non-convulsive) status epilepticus, and resolved with anticonvulsant treatment.

METHODS

The age range of the five patients was 15-74 years. The operations were: aneurysm clipping (three patients) and resections of an oligodendroglioma and a cavernous haemangioma (one patient each). The new focal deficits were: right hemiparesis and aphasia (two patients), aphasia alone (two patients), and left hemiparesis (one patient). The deficits were not explained by CT (obtained in all patients) or cerebral angiography (performed in two).

RESULTS

Electroencephalography showed, in all patients, continuous or intermittent focal seizures arising from cortex regionally relevant to the clinical dysfunction. Subtle positive epileptic phenomena (jerking) occurred intermittently in three patients as a late concommitant. Administration of anticonvulsant drugs resulted in significant improvement within 24 hours in four patients, with parallel resolution of ictal EEG activity. The fifth patient improved more slowly. Two patients relapsed when anticonvulsant concentrations fell, and improved again when they were raised.

CONCLUSIONS

It is suggested that inhibitory simple partial (non-convulsive) status epilepticus be considered in the differential diagnosis when a new unexplained neurological deficit develops after an intracranial neurosurgical procedure. An EEG may help to diagnose this condition, leading to definitive treatment.

Linear estimates of disease progression predict survival in patients with amyotrophic lateral sclerosis

We have shown that linear estimates of rates of disease progression (LEP), derived from isometric myometry [grip or foot dorsiflexion (FD) strength] and forced vital capacity (FVC%), are clinically and statistically significant predictors of survival of patients with amyotrophic lateral sclerosis (ALS) from date of disease onset and, except those based on grip strength, of survival from the date of measurement. We tested these results in 2 additional groups of patients: 1) those who participated in a previously reported Protropin (GH) study; and 2) those enrolled in two other clinical trials (group 2). The LEP were derived and tested as predictors of survival. In a Cox proportional hazards model, LEP based on all measures predicted survival from disease onset in both groups of patients. Using cutoff points determined within the original group to stratify patients in the validation groups into faster and slower progressing subgroups resulted in statistically significant separation of survival curves from disease onset in group 2 for all LEP and in group 1 (the GH group) for LEP derived from FD strength; and, for survival from date of measurement in group 2, when stratified by LEP based on FD strength or FVC%. LEP based on data generated by myometry or pulmonary function studies have now been shown to predict survival in 3 unrelated groups of patients with ALS entering clinical trials. Their precise use in clinical trial design needs to be explored further.

How can physicians and their patients with ALS decide to use the newly-available treatments to slow disease progression?

The 1990s decade has seen the testing of treatments to slow disease progression in patients with ALS. Two such treatments (riluzole and myotrophin) have shown minimal or modest efficacy. Of these, riluzole has been approved for marketing in the United States, in Europe and in other countries. Patients and physicians who are trying to decide whether to use these treatments require background information: (a) to place these treatments in the context of other treatments; (b) to understand the outcome measures used; and (c) to understand the significance of the efficacy these treatments have shown. For example, in some cases treatment efficacy has been shown by some measures, but not others. This paper attempts to assist in this process. In addition, we attempt to show how to integrate objective data with relative or subjective factors, such as patient values, economic considerations, and the role of hope.

Motor unit number estimate-based rates of progression of ALS predict patient survival

We have examined, as predictors of survival in patients with amyotrophic lateral sclerosis (ALS), linear estimates of rates of disease progression (LEP), based on motor unit number estimates (MUNE). Motor unit number estimates of thenar, hypothenar, and extensor digitorum brevis muscles (according to the manual method of McComas), isometric grip and foot dorsiflexion (FD) strength, and forced vital capacity (FVC) were available in 34 patients. Linear estimates of rates of disease progression were derived. Probability of survival was calculated using the Kaplan-Meier method. Motor unit number estimates, LEP based on MUNE, and demographic characteristics were tested as risk factors within the Cox Proportional Hazards Model, using regression techniques. Individually, all MUNE-based LEP were highly significant (P < 0.00005); bulbar onset attained modest significance (P = 0.044). Secondary analysis showed MUNE-based LEP were more significant than regionally concordant function-based LEP. Linear estimates of rates of disease progression based on MUNE may thus predict survival of patients with ALS better than LEP based on function.

Seizure onset from periventricular nodular heterotopias: depth-electrode study

The association between gray matter heterotopias and seizures is well established; whether seizures originate from these lesions is not known. We evaluated three patients with intractable complex partial seizures and periventricular nodular heterotopias (PNHs) with video-EEG monitoring with multiple depth electrodes, including placement in the PNH, to determine whether seizures originate from the PNH. In two of the three patients, all seizures arose from the PNH as low-voltage beta activity. In the third patient, 80% arose from the hippocampi and 20% from the heterotopia. PNHs may serve as an epileptogenic focus in patients with intractable epilepsy.

Linear estimates of rates of disease progression as predictors of survival in patients with ALS entering clinical trials

Maximal voluntary isometric grip and foot dorsiflexion (FD) strength and forced vital capacity (FVC) were obtained in 62 patients with ALS at or close to enrollment into two clinical trials. The agents tested did not slow disease progression. Isometric strength data were standardized, and the worse side was taken. FVC was expressed as a percentage of the predicted value (FVC%). We derived linear estimates of rates of disease progression based on the isometric myometry and FVC measures and on disease duration. Forty one patients were known to have died or to have undergone tracheostomy for ventilatory support. Probability of tracheostomy-free survival was calculated using the Kaplan-Meier method. The measured values, the linear estimates for rates of decline of these values, gender, age at onset, bulbar vs. spinal onset, height and weight were tested as risk factors within the Cox proportional hazards model, using regression techniques. When tested individually, estimates of rates of decline based on all three measures (FD, grip and FVC%) were the only statistically significant risk factors (P<0.005). Multivariate analysis resulted in a 3-variable model (chi-square=75.3, P<0.00001) in which estimated rates of decline of FD strength and of FVC%, and bulbar onset were independently significant (P<0.0001, P<0.0007 and P<0.05, respectively). We conclude that linear estimates of the rate of disease progression till enrollment into a clinical trial may be better predictors of patient survival than demographic data or discrete biologic measures.

Toward earlier diagnosis of amyotrophic lateral sclerosis: revised criteria. rhCNTF ALS Study Group

We modified the World Federation of Neurology (WFN) diagnostic criteria for ALS to facilitate early diagnosis and used these criteria for enrollment of ALS patients in a clinical trial. The criteria developed required lower motor neuron (LMN) involvement in at least two limbs and upper motor neuron involvement in at least one region (bulbar, cervical, or lumbosacral). The EMG finding of fibrillation potentials was required for evidence of LMN involvement. Electrodiagnostic studies, neuroimaging, and laboratory studies were also used to exclude disorders that might mimic ALS. Using these criteria, the diagnosis of ALS was made at a mean time of 9.7 months from onset of symptoms, which compares favorably with the 12-month period cited in the literature. Using clinical assessment at completion of the trial, the diagnosis of ALS was believed to be accurate in those patients entered in the trial. However, pathologic confirmation of the diagnosis of ALS was not obtained. Based on our preliminary experience, we propose that these ALS diagnostic criteria will facilitate early diagnosis of ALS. Future studies should prospectively compare these criteria with the WFN criteria currently in use.

A brief quality-of-life measure for ALS clinical trials based on a subset of items from the sickness impact profile. The Syntex-Synergen ALS/CNTF Study Group

We previously demonstrated a significant relationship (P<0.0001) between maximum voluntary isometric contraction (MVC) plus pulmonary function scores (the Tufts Quantitative Neuromuscular Exam Combination Megascore (TQNE CM)), and the Sickness Impact Profile (SIP) in a cohort of 524 ALS patients. Because the 136-item SIP questionnaire can be difficult to administer in this population, we examined SIP subscales and clinically derived item sets in relation to the TQNE CM in an effort to define a briefer measure of quality of life for use in clinical trials. Two 'Mini-SIP' indices performed as well as the overall SIP in reflecting the impact of muscle weakness on ALS patients' quality of life: a combination of two SIP subscales ('SIP-33'), and a 19-item set of questions independently chosen by a panel of ALS specialists ('SIP/ALS-19'). Either index potentially could be useful in ALS clinical trials. The SIP/ALS-19 is currently being used in a National ALS data base, providing an opportunity to evaluate its utility prospectively against other QOL measures in ALS patients.

Reliability of maximal voluntary isometric contraction testing in a multicenter study of patients with amyotrophic lateral sclerosis. Syntex/Synergen Neuroscience Joint Venture rhCNTF ALS Study Group

Maximal voluntary isometric contraction (MVIC) is becoming widely used for monitoring disease progression in amyotrophic lateral sclerosis (ALS). We evaluated the variability of MVIC in a large multicenter (29 sites) drug trial in ALS. Intra- and interrater variability were assessed twice during the 19-month study. Intrarater reliability increased from the first to the second test, approaching the reliability reported for a single experienced clinical evaluator, but interrater reliability did not. Multiple clinical evaluators in a single site increased the variability of MVIC measurements. Rigorous quality assurance standards and monitoring of clinical evaluators should be incorporated into the design of multicenter studies using MVIC, since low variability is necessary to detect a modest treatment effect.

Placebo-controlled trial of gabapentin in patients with amyotrophic lateral sclerosis. WALS Study Group. Western Amyotrophic Lateral Sclerosis Study Group

We designed a phase II trial to evaluate the efficacy of gabapentin in slowing the rate of decline in muscle strength of patients with amyotrophic lateral sclerosis (ALS) and to assess safety and tolerability. Gabapentin (800 mg) or placebo was administered t.i.d. in a randomized, double-blinded, placebo-controlled, trial for 6 months. We enrolled 152 patients at eight sites in the United States. The primary outcome measure was the slope of the arm megascore, the average maximum voluntary isometric strength from eight arm muscles standardized against a reference ALS population. A secondary outcome measure was forced vital capacity. Slopes of arm megascores for patients on gabapentin were compared with slopes of those taking placebo using a two-way ANOVA. We observed a nonstatistically significant trend (p = 0.057-0.08) toward slower decline of arm strength in patients taking gabapentin compared with those taking placebo (mean difference 24%, median 37%). We observed no treatment effect on forced vital capacity. Gabapentin was well tolerated by patients with ALS. These results suggest that further studies of gabapentin in ALS are warranted.

Comparing composite scores based on maximal voluntary isometric contraction and on semiquantitative manual motor testing in measuring limb strength in patients with ALS

Maximal voluntary isometric contraction (MVIC) is a standardized tool for measuring disease progression in patients with ALS. After normalization, summation, and averaging, it generates composite scores (CS) ("megascores"). In a cross-sectional study, these scores were highly correlated with "average strength" composite scores based on semi-quantitative manual motor testing (SQMMT): r = 0.697 (p < 0.0001). Each 10% difference in the raw SQMMT-CS corresponds to a 0.56 difference in the MVIC-CS (95% confidence limits [CL], 0.38, 0.74). Controlling for height (a highly significant covariate, p < 0.0001), each 10% difference in SQMMT-CS corresponds to a 0.39 difference in MVIC-CS (95% CL, 0.24, 0.54).

Subacute encephalomyelitis presenting as stiff-person syndrome: clinical, polygraphic, and pathologic correlations

A 60-year-old woman presented with stiff-person syndrome (SPS). Treatment with diazepam controlled her painful spasms initially. Two and one-half years after the onset of SPS, new spells of paroxysmal leg jerking and apnea developed. A spell was recorded with simultaneous video and polygraphic techniques that revealed simultaneous firing of motor unit potentials in several muscles (paraspinal, internal hamstring, and abdominal muscles). Apnea was associated with arterial oxygen desaturation. An increase in the dose of diazepam decreased the number and severity of these episodes. Seventeen months later, the patient began to taper the diazepam dose. Shortly thereafter, she had a cardiorespiratory arrest and subsequently died. Autopsy showed small chronic inflammatory foci in the pancreas (some associated with islets) and findings of diffuse encephalomyelitis characterized by perivascular cuffing in the spinal cord, brainstem, thalamus, hippocampus, and amygdala and a dense mononuclear infiltrate in the anterior horns of the lumbar and cervical cord, with relative preservation of axons and myelin. Cell typing showed this infiltrate was polyclonal and reactive. There have been rare cases of SPS associated with encephalomyelitis reported previously. Although the prolonged course in our patient suggested that SPS may have preceded encephalomyelitis, the more likely explanation is that the patient had an unusually long course of encephalomyelitis alone.

Reversible parkinsonism and cognitive impairment with chronic valproate use

Following our initial report of the insidious development of reversible, valproate-induced hearing, motor, and cognitive dysfunction in two patients, we evaluated 36 patients in an epilepsy clinic who had been taking therapeutic levels of valproate for at least 12 months; 29 of these patients were examined according to a prospective protocol. We observed varying degrees of parkinsonism and cognitive impairment, from none to severe. Discontinuation of valproate in 32 affected patients led to subjective and objective improvement on follow-up testing at least 3 months later. Improvement was greatest in patients who were affected most. We conclude that a syndrome of reversible parkinsonism and cognitive impairment may develop insidiously in patients who have been treated with valproate for more than 12 months. The association with valproate may be overlooked due to the insidious onset.

Predictors of outcome of epilepsy surgery: multivariate analysis with validation

PURPOSE

To identify predictors of outcome of epilepsy surgery, using the Duke experience, applying multivariate analysis and validation techniques. To compare the results of different modeling algorithms. Few previous studies have reported multivariate analysis, or validated their results.

METHODS

Records of 116 patients with focal resections for intractable epilepsy from January 1, 1980 through June 30, 1989 were analyzed. Primary outcome variable was patient's condition in second postoperative year: seizure free (except auras), or not. Three predictors of biologic interest were specified a priori for confirmatory analysis. Additional predictors were considered within exploratory analysis. Logistic regression techniques were applied to assess relations with pre- and postoperative predictors. Internal validity was assessed by repeated random selection of training and validation samples, used in conjunction with bootstrap techniques.

RESULTS

By using multivariate analysis, percentage of epileptic EEG activity arising from the site of resection and either imaging localization or lack of use of invasive monitoring were the only statistically significant preoperative predictors for good outcome at 2 years. Presence of seizures within 2 months of surgery was a significant postoperative predictor for a poor outcome. Adding more variables did not result in significantly improved models. Use of validation techniques reduced the degree of optimism in the predictive value of the models.

CONCLUSIONS

Pooling of data from multiple institutions is needed to attain the large sample sizes needed for multivariate analysis with validation.

Relationship of the Tufts Quantitative Neuromuscular Exam (TQNE) and the Sickness Impact Profile (SIP) in measuring progression of ALS. SSNJV/CNTF ALS Study Group

The Tufts Quantitative Neuromuscular Exam (TQNE) is a standardized tool for measuring muscle strength and pulmonary function in patients with amyotrophic lateral sclerosis (ALS). We describe the relationship of TQNE scores to functional disability and health-related quality of life as measured by the Sickness Impact Profile (SIP) in 524 ALS patients. There was a significant relationship (p < 0.0001) between TQNE and SIP scores, both in cross section and over time. TQNE scores strongly relate to ALS patients' quality of life and ability to perform activities of daily living.

A placebo-controlled trial of recombinant human ciliary neurotrophic (rhCNTF) factor in amyotrophic lateral sclerosis. rhCNTF ALS Study Group

Preclinical investigations indicated that recombinant human ciliary neurotrophic factor (rhCNTF) may have potential as therapy for amyotrophic lateral sclerosis (ALS). We evaluated the safety and efficacy of rhCNTF in a prospective, double-blind, placebo-controlled trial in 570 patients with ALS. Patients were randomized to receive 0.5, 2, or 5 micrograms/kg/day rhCNTF, or placebo, for 6 months. The primary efficacy end point was the change from baseline to the last on-treatment value of a combination megascore for limb strength (maximum voluntary isometric contraction) and pulmonary function. Secondary end points included individual arm and leg megascores, pulmonary function tests, an activities-of-daily-living outcome measure, and survival. The four treatment groups were similar at baseline with respect to age, sex, disease duration, and muscle strength values. At all doses tested, rhCNTF had no beneficial effect on the primary or secondary end points. Certain adverse events, as follows, appeared to be dose related: injection site reactions, cough, asthenia, nausea, anorexia, weight loss, and increased salivation. There was an increased number of deaths at the highest dose level. rhCNTF had no beneficial effect on any measure of ALS progression. There were increased adverse events in the 5 micrograms/kg group and increased deaths.

Mechanical trauma as a risk factor in classic amyotrophic lateral sclerosis: lack of epidemiologic evidence

We have examined the relationship between mechanical injuries and the subsequent development of classic amyotrophic lateral sclerosis (ALS) through a critical review of the literature. Only prospective evaluation of a large cohort of trauma victims can provide an unbiased answer to this controversy. However, such an evaluation would be prohibitively expensive, and the results would not be available in our lifetime. The results of retrospective case-control studies are conflicting in part because of biases in the selection of patients and controls, poor definition of the nature and extent of the trauma and its chronological relationship to the onset of ALS, and a non-uniform approach to the collection of antecedent information. More rigorously designed studies show no association of ALS to antecedent trauma. The existing data thus do not suggest that mechanical trauma is a risk factor for ALS. Future case-control studies should conform to a standardized methodology. The critical analysis presented here of the research on the purported connection between mechanical injury and ALS may serve as a model for the evaluation of the role of trauma in other chronic diseases. Application of these methodological principles may bring increased scientific rigor to assessing the frequently litigated question of what constitutes a true trauma sequela.

When is an apparent excess of neurologic cases epidemiologically significant?

To conserve clinical and public health resources, it is necessary to screen reports from the community of an excess or cluster of cases of chronic neurologic diseases for potential epidemiologic significance, ie, to identify those clusters that may have occurred owing to the operation of an underlying etiologic cause rather than to chance alone. Traditionally, the probability that such a cluster has occurred by chance within the reporting community is computed, ignoring the fact that many other similar communities have not reported a cluster. We propose a modified approach that takes this larger universe of communities into account, thereby raising the threshold for potential epidemiologic significance. As a result, the lowest value for the ratio of observed-to-expected cases that may be considered of epidemiologic significance should be increased by factors of 2 for small clusters (one to three expected cases), 1.5 for intermediate clusters (seven to 30 expected cases), and 1.3 for large clusters (60 to 90 expected cases). Consequently, case ascertainment and full field investigations can be reserved for only those reports that, if confirmed, would represent a cluster not due to chance alone. We illustrate this with a case from our own experience.

Epidemiologic correlates of sporadic amyotrophic lateral sclerosis

We evaluated 74 selected patients with amyotrophic lateral sclerosis (ALS) and 201 matched controls for risk factors for ALS by a case-control design and a sequential questionnaire/interview technique to quantitate biographic data. We analyzed occupational and recreational data only for 47 male patients and 47 corresponding patient controls; data for women were insufficient. We used nonparametric analyses to evaluate five primary comparisons of ALS patients with controls: (1) more hard physical labor, p not significant (NS); (2) greater frequency of neurodegenerative disease in family members, p NS; (3) greater exposure to lead, p less than 0.05; (4) more years lived in a rural community, p NS; and (5) more trauma or major surgery, p NS. Men with ALS had worked more frequently at blue-collar jobs (although not a statistically significant difference, p = 0.10) and at welding or soldering (p less than 0.01). These results suggest that there may be an association between ALS in men and exposure to lead vapor. The limited nature of the association favors a multifactorial etiologic mechanism of ALS.

Hyperbaric treatment of cerebral air embolism sustained during an open-heart surgical procedure

A case of cerebral air embolism sustained during replacement of the mitral valve resulted in postoperative coma and seizures. Hyperbaric treatment, begun 30 hours after the occurrence of the air embolism, resulted in good immediate and long-term recovery. Mild deficits of the left hemisphere were present at follow-up 53 days after the embolus was sustained, and lesser, minimal residua were present at 14-month follow-up. Hyperbaric treatment is the definitive therapy for cerebral air embolism. Although it is most effective when administered early, the outcome may be excellent even with late treatment.

Antecedent medical diseases in patients with amyotrophic lateral sclerosis. A population-based case-controlled study in Rochester, Minn, 1925 through 1987

Odds ratios (ORs) were estimated for the prevalence of antecedent endocrine, metabolic, or vascular diseases among 45 patients with amyotrophic lateral sclerosis from the Rochester, Minn, population compared with 90 control subjects matched for sex, year of birth, period of observation, and residence. Hypertension occurred less frequently in male patients with amyotrophic lateral sclerosis (4%) than in control subjects (30%; OR = .10). Because of small population size, no conclusions can be drawn with respect to the following antecedent conditions: thyroid disease (OR = 1.61), coronary artery disease (OR = .58), obesity (OR = .52), diabetes (OR = 1.00), cerebrovascular disease (OR = .21), and peripheral vascular disease (OR = 1.23). The heterogeneity of antecedent thyroid disease makes it highly unlikely that any specific thyroid lesion is causally associated with most cases of amyotrophic lateral sclerosis. Hypertension may be a marker for protective factors against the development of amyotrophic lateral sclerosis in men.

Psychologic and adaptational difficulties anteceding amyotrophic lateral sclerosis: Rochester, Minnesota, 1925-1987

Comprehensive medical records of 45 amyotrophic lateral sclerosis (ALS) patients and 90 controls from the same community, matched by age, gender, and period of observation, were reviewed. Three (13%) of 23 men with ALS, 15 (33%) of 46 control men, 10 (45%) of 22 women with ALS, and 19 (43%) of 44 control women had antecedent psychologic or adaptational difficulties. The proportions of long-standing or serious conditions were comparable in all four groups. However, no man in whom ALS developed had a record of mild antecedent difficulties alone, whereas 3 would have been expected (p = 0.024).

Chronic fatigue syndrome: issues in the diagnosis and estimation of incidence

This article critiques the current working definition of chronic fatigue syndrome. The concerns raised about the current working definition are the following: prolonged or excessive exertion is not addressed explicitly; duration and quality of bed rest are not specified; a socioeconomic ascertainment bias is present; data from history and physical findings are not clearly separated and are relegated to minor criteria; and the rigor of neurologic and psychiatric evaluations is not specified. We propose a flow chart that addresses the possible modes of evolution of chronic fatigue syndrome for patients; this chart may yield more homogeneous subgroups of individuals with this syndrome or enable some patients to avert the syndrome.

Sensorineural hearing loss: a reversible effect of valproic acid

We report 2 patients over the age of 70 who, while on valproate (VPA) for complex partial seizures, developed sensorineural hearing loss. Following discontinuation of VPA for nonaudiologic reasons, the patients reported improved hearing which was confirmed by audiometry. These findings represent VPA-induced sensorineural hearing loss, possibly in preexisting presbycusis.

Clinical neurophysiologic studies in stiff-man syndrome: use of simultaneous video-electroencephalographic-surface electromyographic recording

Three patients with a clinical diagnosis of stiff-man syndrome were studied with simultaneous video-electroencephalographic-surface electromyographic recordings in addition to routine electromyography in order to obtain objective data to confirm their diagnosis, to improve our understanding of the diagnosis of stiff-man syndrome, and to define reproducible clinical and neurophysiologic criteria for the stiff-man syndrome. These patients had the following features of this syndrome: (1) continuous muscle activity that varied with awake and sleep states, posture, passive and active movements, and medications; (2) superimposed intermittent generalized contractions while awake, which continued into drowsiness and interfered with onset of sleep; and (3) abnormal cocontractions of antagonistic muscles. The characteristic findings in the stiff-man syndrome can be recorded by using video-electroencephalographic-surface electromyographic techniques, a useful application of equipment already available in most electroencephalography laboratories. Neurophysiologic techniques can help in elucidating the clinical findings in the stiff-man syndrome. Further systematic study in patients before and during treatment is needed to identify common diagnostic criteria for this syndrome.

How frequently does classic amyotrophic lateral sclerosis develop in survivors of poliomyelitis?

There is a paucity of reports of classic amyotrophic lateral sclerosis (ALS) developing in survivors of paralytic poliomyelitis. We describe a patient with classic ALS and an antecedent paralytic disease thought to have been poliomyelitis from which she recovered completely. If the paucity of ALS preceded by true poliomyelitis is not merely a matter of underreporting, antecedent paralytic poliomyelitis may have a protective role against the development of ALS. This has implications relevant to pathogenesis and to projected secular trends of ALS incidence since the introduction of poliomyelitis vaccines. There is a need to establish the incidence of cases of classic ALS in patients with antecedent poliomyelitis.

Electrophysiological signs of arteriovenous malformations of the spinal cord

A characteristic pattern of electrophysiological changes was found in 24 patients with confirmed spinal cord arteriovenous malformations (AVMs). The AVMs were limited to the thoracic cord in seven, involved the conus and the cauda equina in 10, and involved all levels in six. Of the patients, 88% had at least one definite electrophysiological abnormality: nerve conduction studies showed abnormal results in 43% (10 of 23), needle electromyography in 77% (17 of 22), and tibial somatosensory evoked potentials in 88% (7 of 8). The pattern of involvement was of scattered, multiple, bilateral thoracolumbosacral radiculopathies, consistent with axonal or neuronal destruction, associated with paraspinal fibrillations or abnormal activation of motor unit potentials. Electrophysiological abnormalities were seen in most patients with lower motor neuron clinical deficit. These abnormalities depended on the caudal extension of the AVM, on an arterial supply at T-10 or below, and on the duration of symptoms. In addition to the expected abnormalities in the distribution of the AVM location, four patients had electrical changes at a distance, which may have been due to venous stasis.